A graphene is a two-dimensional crystal composed of carbon atoms, and is a material that has been drawing much attention since it was discovered in 2004. A graphene has excellent electric, heat, optical, and mechanical characteristics, and is expected to be widely applied in the fields of battery materials, energy storage materials, electronic devices, composite materials, and the like.
Examples of the method for producing a graphene include a mechanical peeling method, a chemical vapor deposition (CVD) method, a crystal epitaxial growth (CEG) method, and a redox method. Among them, the redox method, that is, a method of oxidizing natural graphite to produce graphite oxide or oxidized graphite and then reducing the product to produce a graphene is promising as an industrial production method because the method is capable of mass production.
In Patent Document 1, flaky graphite having a large specific surface area is produced by thermally reducing oxidized graphite while expanding and peeling the oxidized graphite at the same time. However, the graphene produced by the thermal expansion and reduction method as disclosed in Patent Document 1 has too large a specific surface area and induces aggregation, and is poor in dispersibility.
Therefore, in Patent Document 2, a compound having a catechol group is used as a surface treatment agent for improving dispersibility.